Reforming naphthas containing deleterious amounts of nitrogen or arsenic



A. RAMELLA 3,069,350 REFORMING NAPHTHAS CONTAINING DELETERIOUS AMOUNTS OF' NITROGEN OR. ARSENIC 3 Sheets-Sheet 1 Dec. 18, 1962 Filed July 14, 1959 A. RAMELLA HTH Dec. 18, 1962 3 069 350 REFORMING NAP As CONTAINING DELETERIOUS AMOUNTS 0F NITROGEN 0R ARSENIC 5 Sheets-Sheet 2 Filed July 14, 1959 MELLA IN V EN TOR.

ANI l LCARE.

REFORMING NAPHTN AMOUNTS 0F Filed July 14, 1959 A RAMELLA 3,069,350 As CONTAINING DELETERIOUS NITROGEN 0R ARSENIC 3 Sheets-Sheet 3 LIQUID'- GAS SEPA zA-roll BFI q ."2.

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BB'R') INVENTOR. AMI L CARE. RAMEL LA Bia/:haw 6 h AGENT c5+ REFon MATE.

United States Patent Otiice 3,069,350 Patented Dec. 18, 1962 3,069,350 REFORMING NAPHTHAS CONTALNING DELETE- RIOUS AMOUNTS OF NITROGEN OR ARSENIC Amilcare Ramella, Woodbury, NJ., assigner to Socony Mobil Oil Company, Inc., a corporation of New York Filed July 14, 1959, Ser. No. 826,989 13 Claims. (Cl. 208-89) The present invention relates to the reforming of naphthas containing deleterious amounts of nitrogen or arsenic in the presence of particle-form reforming catalysts sensitive to nitrogen and arsenic and, more particularly, to the reforming of naphthas containing in excess of 1 part per million (p.p.m.) of nitrogen and 0.002, or more than 0.002 part per million of arsenic in conjunction with naphthas containing not more than 1 p.p.m. of nitrogen and containing greater than 0.002 part per million arsenic, in the presence of particle-form reforming catalysts sensitive to nitrogen and arsenic.

used herein deleterious amounts of nitrogen and arsenic are concentrations of nitrogen or arsenic in the hydrocarbon feed to a reforming reaction zone employing a particle-form reforming catalyst which deactivate the catalyst reversibly or irreversibly to an extent in excess of the reversible deactivation due to the carbon deposited on the catalyst during an onstream period. Nitrogen is a catalyst poison which produces reversible poisoning of the catalyst.A4 That is to say, after a nitrogen-sensitive catalyst has been deactivated or poisoned by contact with nitrogen the activity of the poisoned catalyst can Vbe restored by reducing the nitrogen content of the feed below the level at which the catalyst is poisoned. On the other hand, arsenic causes irreversible poisoning or deactivation of the catalyst. Thatv is to say, the catalyst absorbs arsenic and in an interval dependent upon the particular catalyst the absorbed arsenic reaches a concentration on the catalyst at which both selectivity and activity of the catalyst has' declined to a substantial extent. Arsenic is not removed during regeneration nor by contact with a feed containing little or no arsenic. Consequently, it is necessary to reduce the arsenic content in the feed to a value at which in the useful life of the catalyst, i.e., one onstream period for a non-regenerable catalyst and a plurality of cycles comprising alternate on-stream and regeneration periods for a regenerable catalyst, the amount of arsenic absorbed by the catalyst will not exceed the concentration at which the selectivity and activity of the catalyst is reduced to a substantial extent. Specifically, for a platium-type reforming catalyst comprising 0.1 to about 2.0 percent by weight of one or more of the metals of the platinum group such as platinum and palladium, and a carrier such as a refractory oxide, e.g., alumina, a deleterious amount of nitrogen is more than 1 p.p.m. of nitrogen in the hydrocarbon feed to the reforming unit. A deleterious amount of arsenic when reforming in the presence of the aforesaid platinum-group catalyst is an amount of arsenic in excess of 0.002 part per million in the hydrocarbon feed to the reforming unit.

Preferably, the hydrocarbon feed to a reforming unit employing a platinum-group metal reforming catalyst is essentially free of arsenic. As used herein, essentially free of arsenic designates a concentration of arsenic in a reformer feed which, when said reformer feed is contacted with a bed of reforming catalyst comprising 0.35 percent by weight of platinum on alumina support, is insufficient to deactivate said catalyst within the life of the catalyst,

for example two years, as determined by other factors such as the temperature required to produce a reformate having an octane rating of at least 100 (R4-3 cc.), the yield of reformale, and the mechanical strength of the catalyst.

Reforming is the designation given to a hydrocarbon conversion in which one or more of the reactions, dehydrogenation, isomerization, dehydrocyclization and hydrocracking take place.

It is known that nitrogen like sulfur can be removed from mixtures of hydrocarbons containing nitrogen and/ or sulfur by contact with a catalyst such as a mixture of oxides of cobalt and molybdenum or a catalyst comprising platinum or palladium on a carrier in the presence of hydrogen at elevated temperatures and pressures.

It is also known that arsenic can be removed from mixtures of hydrocarbons such as naphtha by contact with a -nely divided adsorbent such as Attapulgus clay, activated alumina and the like at temperatures of the order of 50 to' 080 F. or at temperatures above the condensation temperature of the hydrocarbon mixture.

It is also known that, while straight run naphthas usually contain less than about 1 p.p.m. and generally about 0.2 to about 0.5 p.p.m. of nitrogen, thermal, TCC, or coker naphthas usually contain 40 to 400 p.p.m. of nitrogen. Under mild conditions, naphtha containing about 10 p.p.m. of nitrogen can be hydrodecontaminated in the presence of a mixture of oxides of cobalt and molybdenum to provide a hydrodecontaminated product or reformer feed containing not more than about l p.p.m.

Under more severe conditions, for example, at about 800 v p.s.i.g., about 850 F. and when circulating about 2500 s.c.f. of hydrogen per barrel of hydrocarbon treated, the nitrogen content of a hydrocarbon mixture containing 200 p.p.m. of nitrogen can be reduced to. not more than 1 p.p.m.

Hydrogenating catalysts having desulfurizing and denitrogenizing capabilities such as a mixture of oxides of cobalt and molybdenum on a support comprising alumina also have the capability of fixing arsenic. The catalyst absorbs or becomes saturated with arsenic at a rate dependent upon the concentration of arsenic in the feed. The higher the concentration of arsenic in the feed the higher the arsenic saturation point of the catalyst. That `is to say, the catalyst can absorb a limiting amount of arsenic.`

Hence, the greater the average concentration of arsenic in the hydrocarbon feed the shorter the time required to reach the limiting concentration of arsenic in the catalyst. Thus, when a hydrocarbon mixture containing 10 p.p.m. of arsenic is contacted with a hydrogenating catalystcomprising about 3 percent by weight oxide of cobalt and about 16 percent by weightv oxide of molybdenum on alumina as a carrier the catalyst will absorb about two pounds of arsenic per ton. Thereafter, the arsenic s not absorbed by the catalyst and arsenic is present in the effluent from the treating unit, i.e., the reformer feed, in concentrations, suiiicient to seriously shorten the life of the platinum-group metal reforming catalyst. Accordingly, to ensure protection of the costly reforming catalyst the cobalt-molybdenum catalyst must be discarded when the catalyst has been contacted with a total amount of hydrocarbon mixture to deposit on the catalyst about 1.5 pounds of arsenic per ton (2000 lbs.) of catalyst.

On the other hand, when the hydrocarbon mixture to be hydrodesulfurized and/or hydrodenitrogenized is essentially free from arsenic the catalyst used for hydrodesulfurizing and/or hydrodenitrogenizing can be reregenerated and not discarded.

Furthermore, some mixtures of hydrocarbons to be reformed are suiciently low in sulfur and/or nitrogen not to require hydrodesulfurization and hydrodenitrogenation but contain suicient, i.e., more than 0.002 p.p.m., arsenic to seriously reduce the life of a platinumgroup metal, reforming catalyst.

Illustrative of hydrocarbon mixtures not requiring hydrodesulfurization and/or hydrodenitrogenation is a straight run naphtha having a boiling range of about a platinum-group metal reformingcatalyst, nevertheless in the endless' task of reducing" the "co'st' of petroleum products means has been sought to reducethecost'of-f' pretreating by removing' arsenic before 'the hydrocarbon mixture to 'be hydrodesulfurized 'and/or hydrode'nitrogenized is contacted with' the hydrogenating catalysti Several prior art disclosures rec'omrneridoxidizing the arsenic 'or otherwise 'converting'the arsenic' to 'a more readily removable form. Among' the'se'disclosures arethose contained in U. S. 'Patents No's. 2,769,770; 2,778,779;

2,779,715; 2,781,2 97gand 2,782,1'f1. German patent application No. 1,042,804 (published vNovember' 6,v

1958) recomme'uds'the 'addition of to' 15 percent by weight' of boron oxide "to'the'cobalt4molybdeum'type desulfurization catalyst .to improve"desulfuri zation and to improve the removal of 'nitrogen 'and' arsenic compounds. The 'rcmovaljofars'enic 'compounds'by contact' with partially deactivated platinum 'reforming catalyst at temperatures ef 'the' 'orderef 255V Ffte about 795" is disclos'edlin' Italian `Pa"tent"No"."'525,'3"88 (publishedV May 4, 1955):`

It' 'is now" props'ed jt"gedanst.fanarsenieenfaiairrg prior to hy'dr'odec'c ritan1`inatior1' in the 'presence `ofthe more costly hydrodecontarnination' catalyst 'or to' contact an arsenic-containing hydrocarbon mixture 'with' a-h'y'" avoiding saturation of relatively cos tly hydrogenating catalyst. The amine-containing effluernstnen contacted with "a` cheap. adsorbent A'ata' temperature of -atleast' l arsenic en the cheap adsorbent Thereafter', ureflayers-f" carbon' mixture is "hydrode'contarn ed, sulfurized and/ or'jhydrodenitrogenized."

instances the pretreated 'hydrearben'-nnxture't'b refermedie.,

the'j reformerfe'ed musr'jeorrtairrnt more" an"'1 p.p.m. of'ni'trogen' and be es's'entiallyf-ffree" from arsnic'," i.e;,

canning not more than 0.002 -p.p;m. (2 'p p; hinten): of

arsenic' 'and preferably less.'

CASE I t- Thus;"arst hydrocarbon mixture containing in excess of `l0p.'p.m. ofnitrogen 'but-not suflicient' `arsenic to T seriously shorten the, life ofthe"hydrodecontaminating catalyst, i.e., containing not more than 0.100 p.p.m. of arsenic, can be hydrodecontaminatc'd in the' 'presence' of hydrogen and a hydrogenating 'catalyst' having hydro de'slfu'rizing and/or' 4hydrodc'z'nitrog'enizing capabilities,

c g., Aa mixture 'of oxides vof cobalt 'and molybdenum on a refractory oxideisupport such 'as alu'r'r'iina''to"pr'oducc a pretreated' first 'hydrocarbon mixturecoiitaining'not more than 20 'p.p.m.' of nitrogen which is"esse'ntia'lly'l free from arsenic. The pretreated 'r'st'hydr'oearbonmixture is mixed 'with a'second'hydrocarbon mixture containing less nitrogen'than `the `afor`esai`d-`pfetre-ated first hydrocarbon mixture topio'vide a blend containing -not y more'than 1 p.p.m. of nitrogen which is 'essentiallyfree from 'arsenic'.

The 'aforesaid second'hydrocarbon-mixture can be untreated naphtha containing not more than 0.5 p.p.m. :of

nitrogen and essentially free from arsenic, which when mixed in the proportion of` volumes 4with 5 volumes of the'afores'aid pretreated first hydrocarbonmixture containing not more than 10 p.p.m. of nitrogen provides a blend reformer feed containing not more than l p.p m.

of nitrogenv which is essentially' freel from arsenic( Alternativcly, the second hydrocarbon mixture can bel sufliciently low' in nitrogen that when mixed withthe clay preferably at temperatures of about- 50 `to about" V F. to reduce thearseniccontent of. the s aidsecond hydrocarbon mixture to a level suchthat when mixed with the aforesaid pretreated first hydrocarbon mixture to form a blend reformer feed, the blend. reformer feed is essentially free from arsenic, i.e., contains not more than 0.002 p.p.m. of arsenic and not more than l p.p.m. of nitrogen.

Many mixtures of hydrocarbons such as lthermal naphfy thas to-be reformed not only contain excessive, i.e., more` than -20 p.p.m. of nitrogen -bt in addition containA v amounts of arsenicin excess of that which does not seriously shorten the lifeu of-f the catalyst employed foire-n ducing the nitrogen content of the hydrocarbon mixture to not more than 20 p.p.m. Amoun'tsofarsenic .inexf ce ss .zof-.that which can .be tolerated-aregreaterl than 0.05 to; but not more than, 0.100 p.p.m. of arsenic.- In a that event. the .high' nitrogen first hydrocarbon mixture lil'gewisejisvrcntacted withl -a solid adsorbentasuch` as. Attapulgus clay prior to hydrogenaton.

Alternatively, the high nitrogen first hydrocarbon mixture is-contacted with a hydrogenatingA catalyst;in the presence for hydrogen at a temperature -belowthe de composition temperature of arsine, for-:example atta pressures orr1ewhatv higher than that at- .which-.the1first--, hydrocarbon mixture ishydrodenitrogenizedand/orhy-q` about l to 10 and at a hydrogen circulation ofA about- 35'0fto'about 1000 standard cubic feet. per barrlofr-iirstw hydrocarbon mixture. The einuent of therst hydrogertza,l tion is then .-contacted at a temperatureat Whichnarn decomposes to arsenic andhydrogenin contactgwith a solidadsorbentsuch vas Attapulgus clay.= Suitable ltem- .peratures lfor the decomposition ofarsineare 'those in f:

such that when mixed with a second-treated hydrocarbon mixture the blend is essentially free yfrom arse-ric anda contains not more than l p.p.m. of nitrogemI It is another object-of the present invention to treat a first-hydrocarbo'nmixture containing more than 10 pp m.- of.;-: nitrogen and containing arsenic in excess ofv0.002 p.p.m..l tofreduce' the nitrogen content thereof to not more 'han-- 20 p.p.m. and the arsenic content toa 1evel such that'. when mixed wi'h a-treated second hydrocarbon--mix-r: ture to form ablend the Vblcndis essentiallyzfr'ee'frcm arsenicand contains not more than 1 p.p.m. of.ni'ro gen; Itis a further object of the'present 'inilentim to:f first sub'ecta lrst hydrocarbon mixture containing inore than 0.002 p.p.m. of arsenic to hydrogenation to.p'o duce arsne, to decompose the arsineand abscrbthe' arsenic produced and in a second treatment hydrodenitro genize the -first hydrocarbon mixture to 'produce 'a pre-ftreated :first hydrocarbon mixture containing-rot Vmore than 1 p.p.m.vof nitrogen, to contact a second ihydrocarbon mixture containing not more than 1 p.p.m.: of nitrogen and more than 0.002-.p.p.m. offarsenicwith'.'a-'v` solid adsorbent to produce a treated second hydrocarbon-f:

mixture which, when mixed with the aforesaid pretreatedl first hydrocarbon mixture in the ratio of to 95, preferably 50 to 90 parts of the aforesaid treated second hydrocarbon mixture with 95 to 5, preferably 50 to l0' parts, of the aforesaid pretreated first hydrocarbon the blend so produced is essentially free from arsenic, i.e.,.

contains not more than 0.002 p.p.m. of arsenic and contains not more than 1 p.p.m. of nitrogen. The prefent invention contemplates reforming the blends produced as described hereinbefsre in the presence of hydrogencontaining gas and nitrogenand arsenic-sensitive particle-form reforming catalyst.

The owsheet of FIGURE la is illustrative of the` treatment of a first hydrocarbon mixture containing in' excess of p.p.m. of nitrogen and essentially free of arsenic or containing insutiicient arsenic to require re`l duction thereof to provide a blending component which is essentially free of arsenic. FIGURE 1 also illustrates.

the treatment cf a second hydrocarbon mixture containing less than 1 p.p.m. of nitrogen but a ccncen rat'on of arsenic in excess of 0.002 but not in excess cf 0.100;

p.p.m.

'The owsheet of FIGURE 1b is illustrativi.n ofthe,

treatment of a first hydrocarbon mixture containing in'A excess of 0.002 p.p.m. of arsenicand in excess of 20;

p.p.m.'of nitrogen wherein the arsenic is hydrogenated'` at a temperature below 440 F. to produce arsine, the: arsine is decomposed at a temperature of at least 440" F. and the arsenic so produced deposited on a solidA adsorbent andthe efiiuent of the absorber contacted at a temperature of at least 600 F. :with a hydrogenating'.`

catalyst inthe presence of hydrogen-containinggas `tov hydrodenitrogenize the arsenic free, i.e., containi g less; than 0.002 p.p.m. of arsenic, first hydroarbon rrixture to reduce the nitrogen content to not more than 20 p.p.m.'j

and produce a suitable blending component for a .re-lf former blend feed.

FIGURE 2 is a flowsheet illustrative of the reforming of a reformer blend feed produced in accordance `with the principles illustrated in FIGURES la and 1b employing an arsenicand nitrogen-sensitive catalyst such as a platinum-group metal reforming catalyst, e.g., a platinum reforming catalyst comprising about 0.2 to about 2.0 percent by weight of platinum and about 0.1 to about 0.8 percent by weight of a halogen such as uorine and chlorine on a support such as alumina.

The high-nitrogen naphtha can be hydrcdeccntaminated in the presence of a hydrogenating catalyst having hydrodenitrogenizing capabilities under conditions set forth in Table I `to produce a hydrodecontaminated mphtha having a nitrogen level which when blended with'l the percolated naphtha will provide a blendcontainng.

not more than 1 p.p.m. of nitrogen.

Table I Catalyst About 1.5 to 3.8 wt. percent cobalt oxide; about 7 to 16 wt. percent molybdenum oxide carrieralumina. Pressure, p.s.i.g 100 to 1000. Hydrogen, s.c.f./b 350 to 2500. Space velocity, v./hr./v 1 to 10. Temperature, F 600 to 850.

6 Table Il -Treatiriggtemp., F 50-180.

B;bls. /ton 10,000 to 40,000.

'llllustrative of the present invention is the hydrodecontamination of a thermal naphtha containing about 0.025 p.p.m.of arsenic and about 24 p.p.m. of nitrogen under -conditions toproduce a hydrodecontaminated naphtha containing 0002 p.p.m. of arsenic and not 15 p.p.m. o f 4nitrogen under the conditions set forth in Table III.

- Table 111 Pressure, p.s.i.g 450 Temperature, F 675 Space velocity, v./hr./v 2.3 Hydrogen/ b., s.c f 2000 A low-nitrogen, high-arsenic, straight-run naphtha containing 0.5 p.p.m. of nitrogen and 0.0200 p.p.m.-'of arse-` nic was contacted with rAttapulgus clay under the condi--4 tions set forth in Table IIgto produce a perc'olated naph-- tha containing 0.5 p.p.m. of nitrogen and 0.002 p.p.m. of

arsenic. l i

The aforesaid percolated naphtha was mixed with the aforesaid hydrodecontaminated naphtha in the ratio rof- 20 volumes of the former and 80 volumes of the 'latter lto provide a reformer feed blend naphtha containingl 3.5.

p.p.m. of nitrogen and about 0.002 p.p.m. of arsenic.

' Illustrative of the method of the present invention is' the owsheet of the drawings la, 1b, and-2.

'--A first hydrocarbon mixture containing in excess of 20 p.p.m. of nitrogen isdrawn from a source not shown 'through pipe 1 bypump 2. (See FIGURE 1a.) Pump` 2- discharges the first hydrocarbon mixture into pipe 3.-

Wh'en the first hydrocarbon mixture contains more than 0.100 p.p.m. of arsenic the first hydrocarbon mixture' flows through pipe'3 (valve 4 open; valveS'closed) to absorber 5. The first hydrocarbon mixture flows downwardly through absorber 5 in contact with solidA adsorbent such as Attapulgus clay to pipe 6 and thence to pipe 9.: When the first hydrocarbon mixture contains appreciably less Lthan 0.1 00 p.p.m. of arsenic the absorber 5 is by-passed. That is to say, with valve 4 closed and valve 8 open the first hydrocarbon mixture Hows throu'gh pipe 7 to pipe 9. When the arsenic content of the rst hydrocarbon mixture is too high to permit 'the total ow of first hydrocarbon mixture to by-pass absorber 5, butA not in excess of 0.1 p.p.m. of arsenic, the flow through pipe 3 and the fow through pipe 7 is regulated sothat the blend of the absorber efuent and the portion of the first hydrocarbon mixture owing through pipe 7 containsV not more than 0.050 p.p.m. of arsenic.

The first hydrocarbon mixture containing not more than 0.050 p.p.m. of arsenic ows through branches 10 and 12 of pipe 9 to liquid absorber 14. In liquid absorber 14 the first hydrocarbon mixture is contacted with gas containing C4 and heavier hydrocarbons iiowing from liquidgas separator 31 or from separator 31 and stripper 40 through conduit 33 and branches thereof 34 and 36. The volumes of first hydrocarbon mixture flowing through branches 10 and 12 are controlled by valves 11 and 13 respectively. The volumes of gas flowing through branches 34 and 36 are controlled by valves 35 and 37.

The volumes of first hydrocarbon mixture liowing through branches 10 and 12 and the volumes of gas fiowing through branches 34 and 36 are regulated to strip substantially' all of the oxygen, water, and heat exchanger depositV precursors from the rst hydrocarbon mixture and t0 7, Strip substantially all of the Gland heavier hydrocarbons from the gas. A temperature within the limits of about 100 tch-abouti 1509' F.' -usually is` maintainedinfsliquid absorber 14;`

Thelstripped lgas ows from liquid absorber 14 through conduit -54-to-lmeansefor'therecovery of sulfur and ammonia-andiultimately-to1=therefinery fuel main, directly tty-th'e'refin'ery1 fuel-mainor-to other processes capable of using gas containing hydrogen of this concentration.

The stripped iirst hydrocarbon -mixture ows'-througli. pipe 15 to hea'texchan`ger'1'6 wherethestripp`ed""tirsthydrocarbonamixtureis in-LA indirect .hea-t exchange ..rela tion -wit-hfth'e eiuentof. hydrodecontaminator23..owingi fromeheat exchanger18 through'xonduit 25. From heat.. exchanger 16;, the -iirst hydrocarbon mixture. ows through. pipe '17 to` heat-` exchanger. 18 where `the lrst, hydrocarbon mixture `is in indirect-.heat exchange.- relation with the.. hydrodecontaminator effluent owing therefrom through conduit 24.

From heat exchanger 18 the rst hydrocarbon mixture 20 mixtureowsfthrough conduit-22ftofhydrodecontaminator 25 23,- Atta gpoint -in= iconduit' 2.2 intermediate to heater 21e andfhydrodecontaminatorhydrogenecontaininggasa-for.: examplefreeycle-,gas-owingfrom i a-f: reformer: through conduits P42 =and441orta mixture of trecyleegasrand stripper overhead tiowng from stripper 40'through @con- .30.

duits 33 and 46fto-conduit-f44 is mixedwith fthe-tirstfhydrocarbon fmixture ztofmaintainathehydrogen-circulation. setforth..r hereinbefore-.- y

. In hydrodecontaminator-.ZS thetiirsthydrocarbonfmixture and=l hydrogen-containing, gas rowf ..downwardly-,A in co'ntact with a= hydrogenatingY catalyst t having .hydrodenitrogenizing fcapabilities.' The-f efuent of` hytlrodecon# taminatonl, Hows-through. conduit 24 .'totheat exchanger laaandr thence-.through t :,Qn1:luit 25j.toj heatffexchangerrl'tif.. asgpreviously ldescribed.:i From;heataex-cl1anger4 161.-,-thef hydrodecontamina'ton.- eiuent .-ows .through .conduitc261f to Aheatexchanger` 27-A where-theahydrodec:ontaminatonv efuentis infindirect Vheateexchillgelelationfwith the eHu-jent condensate iiowingt. -from gas-liquida,- separator- 3h decontaminatorefuentflows-.through conduit -28to cooler- 29-wherethe .eiuentfis cooled =to-a ytemperature .atiwhich` C41' and heavier-hydrocarbons' 'ares-condensed. at the pres surefexisting inlfseparatorl.-

From -cooler 29fthe Ihydrodecontaminator eiuentiflows through -conduit 30-to liquid-gas-separator 31.V In separator. 3-1 a ventgasl comprising .the hydrogen,. hydrocarbonsylhaving: vless than fourcarbomatoms,l hydrogen= sulfide; andfammonia ofthe hydrodecontaminator-eiuntseparatevfrom the CQ: andfheavienhydrocarbonsaof.theeiuent. The eiuent vent-gasows-from separator 31` throughconduitsfZ and 33,.and..branches341-.and-.36 toJ liquid absorber 14` and thencethrough-conduit-54 .as de# scribed hereinbefore;

The eiuent condensate comprising. C4-;.-.and heavier hydrocarbonsyand trace concentrations ofhydrogen sul" fide and ammoniafows from separator 321 through pipe` 38 lto heatexchanger 27 and'.thence-throughgpipe-39 tostripper 40.

In' stripper t0-the* effluent-condensate` is contacted with a.stripping1.gas; erg.,.recyclegas-Ifrom-f a-reformeratA atemperature,l maintained for exampley bysteam` coill 41,.- at which' trace concentrationsfof. hydrogen suldeand ammonia areremoved.. A suitable-temperaturefat'which- C4 and lighter hydrocarbonsare volatile isfmaintained-in stripper 40.v Recycler gas owing from the reformer. (-FGURB 2, -conduit-R-42): through-conduitP- 42`under contro1-of-valve43 is introduced into `stripper `40. The= stripping gas-ows upwardly to conduit33 and thence toliquidabsorber.14.. .A` partor-all ofnthestrippinggas.

can be diverted through conduit 46 under control of valve 47"`to'con'duit '44' and flow thence' to hydrodecont'a'minator' 235 `From` stripp'e'r"40 the stripped condensate ows through'pipe45 to'pipe'Sl wherethe condensate 'is'mixed with treated" second hydrocarbonmixturein proportions' to produce' a' blend reformer feed containing' not' more than l.p.p.m.' of nitrogen and essentially free from arsenic,

i.e;, containing'not more"than'0.002p.p1m. of iarsenic.

A second hydrocarbon'mixture'containing substantially* les`s"tha'n 1 p.p.m'., say about 0.5' p .p.m:, of nitrogen but containingjmore than' 0.002 p.p'.m. of' arsenic' is drawn" from a'source notsli'own through p-ip'e.46by pump 47. Pump 47 discharges the second hydrocarbon mixtureinto" pipe 48'. The' second 'hydrocarbon mxture'ows' through pipe-48 to'. solid absorber'50. In.so1id"ab'sorber'50'the secondhydrocarbon mixture-is"in contact with a solid adsorbent vsuch a's' Atta'pulgus' clay which absorbs the" arsenic-containingcompounds. 111e eiuen't fromsolid absorb'er'50`ows through'pipe'Sl.. In pipe 51`the effluent' of absorber' 0"is`mixed with the' stripper' bottoms to provide'a' blend"reformer`fed containing not'morethan" 1 p.'p:m: ofnitrogen'and vessentially "free from arsenic;

When the first hydrocarbon mixture not only contains"- gen; .ifea` more 'th'an 20ppm. of" nitrogen, napnthafis" drawn 'from a 'snurce'not"shown'ttrrbugh' pipe 1'151b'y" pump' 116i' Pump-116 `dischargesthenrstthydrocartmn' mixture' intolpipe' 117 'through .whicli'it Hows -to branch'es 118111111 E119 under-"control dr'valves '120 -andfl'z'i"respectively, tojliqud" absorber 122'.' In liquid *absorber'lz* tlier's'tfhydrocarbon mix'tu're .is 'contacted' 'with'. strip'r'ii'ng'4 gas; eg., .hydrogen-containing g'as ow'ingfromliquid-gas separator" 31A (FIGURE '1a)' through' conduit 33 and'j branches"34"and36under`control of valves'SSiand 37 respectively. The ows of first hydrocarbon mixtre"an'd"V otifstippin'gf` g''s aref regulated'1 'a'n'd i proportioned as "d'es'o'rlbe'dihereiribeforein' conjunction with the' description offliquid absorberglt; Gslis-v'e'nted fromlabsorber 107i' through-conduitflzv.

rStrippedstirstfhydrocarbon mixture -flows fromra'bsorberf 107 through 'piper'- 124v yto-fhe'atZ exchanger. v16.1 where" the. stripped-.first- .hydrocarb'on mixtureis.: in indirect :heat: exchangerelation .with the -etliuent of the-hydrodecontami-l nator 23'.- From heat. exchanger 16 thestripped first hy.-f4 drocarbon.. mixture owsthrough conduit.125 to. arsenic hydrogenatorr126. At a .point in conduit'125 intermediate v,to heat exchanger 16 and to arsenic hydrogenator 126l hydrogen suflicient'to `maintain a'circulation offabout'250 to about'1000 standard cubic' feet per barrel of first hydrocarbon-mixture "isintroduced i into conduit '125. Usually recycle 'gas wingfrom' a'reforrner"through conduit 44' (FIGURE la) and conduit- 127 under control of vali/'e 128 is employed.

The rst hydrocarbon mixturefis usually heated in heat exchanger 16 to a temperature so that when mixed Iwith the recycle gas the mixture has a temperature not-higher than--about.400 F. The mixture of first hydrocarbon mixture and hydrogen-containing gas ows downwardly through arsenic hydrogenator 126 in contact with a hydrogenation catalyst,' for example, a mixture of oxides of cobalt and molybdenum on alumina. In arsensic hydrogenator 126 the arsenic compounds in'the virst hydrocarbon mixture are'converted to gaseous arsine which at' temperatures below about 440 F. is not decomposed. The effluent fromhydrogenator -126- ows through con-- duit 129 to heat exchanger 18 Where the hydrogenator eflluent is' in indirect heat' exchange relation= with the efuent` of hydrodec'ontaminator- 23' llowing therefromthrough'conduit 24. The' temperature'of .the hydrogenator elu'ent is raisedto above about 440 F; in heat exV` changer 13. When nec'essary'to-rnaintain' a temperaturef of at least 450 Rin solid absorber. 131 hot hydrogen-- 9 containing gas in amount to provide with that introduced into conduit 125 a total of about 500 to 3000 standard cubic feet of hydrogen per barrel of first hydrocarbon mixture is introduced into conduit 130 at a point contiguous to the vapor inlet of solid absorber 131. Thus, for example, hydrogen-containing recycle gas is diverted from conduit 44 through conduit 132 under control of valve 133 to heater 135. In coil 134 the heat-carrying medium, in this instance hydrogen-containing gas, i.e., recycle gas, is heated to a temperature dependent upon the temperature and volume of the hydrogenator efiiuent andl the volume of heat-carrying medium to provide a mix-- ture having a temperature of at least 450 F. The heated heatcarrying medium flows from heater 135 through conduit 136 toconduit 130 where the heat-carrying medium is mixed with the effluent of hydrogenator 126. Preferably, solid absorber 131 is placed as close to heat exchanger 18 as convenient to reduce the deposition of arsenic in the transfer line. The hydrogenator eliluent tiows into solid absorber 131 through conduit 130 at a temperature in excess of about 440 F. In contact with the solid. adsorbent, Attapulgus clay, for example, and at a temperature in excess of 440 F. the arsine in the hydrogenator eliiuent decomposes to deposit arsenicon the adsorbent. The eiuent of solid yabsorber 131 fiows'theref from through conduit 137 to coil 20 in heater 21 where the efliuent of the -solid absorber 131 is heated to hydrodenitrogenizing temperatures as described hereinbefore,

In the event that the eiuent from solid absorber 131 contains-not more than 1 p.p.m. `of nitrogen in addition to being essentially'free fromarsenic as defined hereinbef; fore, the eiuent from solid absorber 131 is a suitable .re-

formel, feed or reformer feed-component. 'In the fore-4 going circumstances, the effluent from solid absorber 131 is diverted through conduit 138 under control of valve.

139 to the suction side of pump 52 (FIGURE4 1a).

@On Athe other hand, when the eftiuent from solid .ab' sorber 131 although essentially free from arsenic as -defined hereinbefore has a nitrogen concentrationsuchthat whe'nblendedjeven in the ratio of 5 parts of absorber efuent with 95 parts of a second hydrocarbon mixture having a lower concentration of nitrogen, say 0.2 p.p.m.`

of nitrogen, the resultant blend contains more than l p.p.m. of nitrogen, i.e., when the absorber eiuent contains more than about 19 p.p.m. of nitrogen, the absorber effluent liows through conduit 137 to coil 20 in heater 21.

In coil 2i) the solid absorber efiiuent is heated to hydrodenitrogenizing temperatures within the limits of about 600 to about 800 F. The heated solid absorber effluent flows from heater 21 through conduit 22 tohydrodecontaminator 23. In hydrodecontaminator 23 the solid absorber effluent is contacted with hydrogenating catalyst having hydrodenitrogenizing capabilities such as the. mixture of oxides of cobalt and molybdenum described hereinbefore. From hydrodecontaminator 23 the effluent thereof ows through conduit 24 to heat exchanger 18, through conduit 25 to heat exchanger 16, and through conduit 26 to heat exchanger 27, liquid gas separator 31, and stripper 40 as described in conjunction with FIGURE la. The bottoms of stripper 40 comprise a blending component for a blend reformer feed as described hereinbefore, said blending component being essentially free from arsenic and containing not more than that amount of nitrogen which when blended with a second hydrocarbon mixture in the ratio of to 95 parts of said blending component to 95 to 5 parts of a second hydrocarbon mixture to form a blend reformer feed the blend reformer feed is essentially free from arsenic as defined hereinbefore and contains not more than l p.p.m. of nitrogen.

Alternatively, a splitter can be used in place of the stripper illustrated. In that event no hydrogen-containing gas is introduced into the splittenand all of the ex-l cess reformer recycle Vgas flows directly to conduit 44 and thence-to conduit 22. -That in excess of the amount re- 1t) quired in hydrodecontaminator 23 is diverted through conduit 46 to conduit 33 and absorber 14. Additionally, the splitter overhead flows to gasoline blending rather than baci: to conduit 33.

It is to be noted that stripper overhead can also be diverted from conduit 33 through conduit 46 under control of valve 47 to conduit 44 and thence to pretreater 23. The percolated second hydrocarbon mixture is obtained for blending as follows. A. low-nitrogen, high-arsenic naphtha, for example,'i.e.', a straight run naphtha is drawn from a source not shown'through pipe 46 by pump 47.

Pump 47 discharges the high-arsenic, low-nitrogen naph-' tha into pipe 48.` 'Ihe high-arsenic, low-nitrogen naphtha .is pumped through clay tower 50 in upward or downward flow under conditions within the ranges set forth hereinbefore. The percolated naphtha leaves clay tower 50 through pipe 51. The percolated naphtha in pipe 51 is jnixed with the hydrodecontaminated naphtha flowing through pipe45 to provide a blend reformer feed contaning notl more than l p.p.m. of nitrogen and essentially` reformer feed into pipe 53P"at a pressure in excess of the pressure existing in reforming reactor 71 `(FIG- una 2).

AV'1he .,bl end naphtha flows through pipes 53-P` and 53-RY to heat exchanger 64. In heat exchanger 64 the blend naphthais in 4indirect heat exchange relation with the -effluent from reactor 81 (final efiuent). From heat exeliiuen't.' Fro'rnheat exchanger 66 the blend naphtha flows' through conduit 67 'to coil 68 in heater 69. At a point"` intermediate .to heat exchanger 66 and to heater 69 hydrogen-containing gas such as recycle gas flowing from separator 91 through conduit 55 to the suction side of compressor 56 and from compressor 56 through conduit 92 ismixed with the blend naphtha in the ratio of about 4 to about 20 mols of hydrogen per mol of naphtha to form a reformer charge mixture. The reformer charge mixture is heated in coil 68 to a reforming temperature within the range of about 825 F. to the maximum ternperature at which the reforming catalyst is not irreversibly deactivated.

For a reforming catalyst of the following composition thereforming temperature is within the range of about 825 F. and about 980 F. dependent upon the activity of the catalyst, the operating pressure, space velocity, and the required octane rating of the C5+ reformate. In general, for a platinum-type reforming catalyst comprising about 0.3 to about l percent by weight platinum and about 0.3 to about 0.8 percent by weight of chlorine reforming conditions are as follows:

Reforming temperature, F 825 to 980 Pressure, p s g 100 to 1000 Space velocity 0.5 to 10 Hydrogen-to-naphtha mol ratio 4 t0 20 The heated charge mixture flows from heater 69 through conduit 70 to reactor 71. The charge mixture ows downwardly through reactor 71 to conduit 72. The first reactor effluent ows through conduit 72 to coil 73 in heater 74. In coil 73 the first reactor efiiuent is reheated to a reforming temperature lower than, higher than, or equal to that to which the charge mixture was heated. The

heated first reactor eiuent flows from heater 74 through* conduit 75 to, reactor 76. The first reactor effluent liowsv downwardly through reactor 76 to conduit 77. The secfeed hows through pipe 51 to the ond reactor efuent ows through conduit 77 to coil 78 in heater 79. In'heater'79 'the second reactoreluent'is' reheatedto'a reforming temperature. The heated second reactor efliuent ows from heater-79"through conduit 80l to reactor 81. The reheated secondreactorefuent hows4 downwardly through reactor 81 to conduit 82. The final reactor efllu'ent ows through conduit 82-`toheat lexchanger 64.' From heat exchanger 64 the nal eliiuent flows through'conduit '83* to heat exchangerA 84 -where Ltheeiinal eiuent is in' indirect heat'exchange'relation-'with'the con-- densate from separator 91 'owing through pipee96. From= heat 'exchanger84 the ''nal 'eiiientows through con duit '85 to heat 'exchanger 86. From 'heat-'exchanger'Sa'the'l ilal' ei'uent-- ows through conduit 87 :to 1heatvexchanger 661 From"heat'eXchanger' 66- the linal'eihuentV Hows-i through `conduit 88 v to cooler 895 eIn'cooler 89 tlreinaheill'uentislcooled to atempera ture 'at which'Cg'and heavier *hydrocarbons` are condensed" at the "pressure"exis'ting in -separatorV 91. From 'cooler J89 i the'iinal eiuer'rt 'ows through condit9lto-hglrzpres-f sure separator'91. In high pressure separator 91"th'e"con': de'nsed' final' euentisfsepara'ted" from the uncondensed e nal'elnent? The-uncondens'ed Eiiial"effluentg tiovs'e'rcm high-pres# surerseparatr' 9'1 througtconduit'ss ref "the suction sideofl coIn'pressLJ'rS"A Cmp'ressorSfdischarge's th'e-"l1n'con'` densed nal eiuent, i.e., reformer recycle gas into-"coin" duit 92 a't a`press'ure`n excesofithatinreactor71 A portion of uncondns'ed Liixal *elu'entl usually :about: equalf'to'the 'ga's"'m`adefin the reformr'rgreacti'on; isf` diverted throughecnd'itrtZlR; under-'control tofvalve 93 to.conduit 42-P (FIGURE 1a) and pretreater 23and7orf hydrogenator 126`V asr` described"hereinbefore: `The^balance' ofth'e 'recycle'gas ows"through"conduit 92`to con-L duit 67 whereit is mixedwith' the reformer feed' naphth'a" blencra's previously' 'described' herein.

exchanger- 84. In heatex'changer" 84 the condensed'nal'f eiiiu'ent is'in indirect h'eat' exchangerelation-withthe ina'l "efuent winglieretothroughconduit V83." From" heat "exchanger 84"theraw reformateeows through pipe" 113"to"stabilizer 97. Y.

In' 'stabilizer 9T" light hydrocarbons areta'l'ren as' over# head'through'ppe 98"to` cooler 99. Theoverhead"is" cooled'in"codler.99to aternperatureat which@ hydro#- carb'ons' are condensed The' cooled overhead: hows through"plpe"100*to accumulator 101. Fromaccumula tor'1 the'uncondensedoverheadj ile?, C3 and 1ighterhy--- drocarbons, ilows through pipe 102 and thenceto-the'gas'x recovery-main: The'condensedbverhead; C4 and heavier hydrocarbons; ows fromzaccumulton'lOl through-pippe- 1.03 to" the'` suction"'side"'of "pump 104i charges a partoft'he condense'doverhe'a'd int'oppelOS" as reux in stabilizer97. 'l-he'portion'ofithecondensed overhead in excess of'tha't required forreuxeows. from4 103' through pipe' 1'0`6"-under"control'ofvalve 107 to'recovery OPC4 hydrocarbons.

stabilizer-97 through vpipe 108as "stabilized `C5+A reformate;y The balancezandeminor portion-ofthe stabilizer bottomsx owsethrough pipe -109-to-heat-exchanger 86 where the". stabilizer bottoms -isin indirect heat exchange lrelation A withthe finalieiuentowing from heat exchanger` 84 throughconduit 85. In heat exchanger 86the stabilizery bottomsis heated to a -temperatureat whichC4,and lighter. hydrocarbons are volatile. Fromlheat exchanger 86 the stabilizer bottomsilows throughpipe 110 to thesuction side of .pump 111. Pump 111 dischargesthe heated stabilizer bottoms into pipe 112 through which. the heated stabilizer bottoms ows to stabilizer 97. Any other means. ofsmaintainingthe required temperature in stabilizer 97' can .be .substituted for.. the reboiler illustrated.

I claim:

1; A-methodof'removing arsenic'frorn a Vhydrocarbon mixture which-comprses-in a reaction zonecontacting'a hydrocarbon mixture lcontainingarseni'c with hydrogenat ing catalyst under conditions 'of pressure,- liqud hourly spacevelocity, hydrogen circulation, and at a tempera-- ture `not higher than about 425 F. at which arsenic is'- convertedto a volatile derivativeof arsenic, withdrawing from said reaction zone'at'a temperature below 440' F. a' reaction zoneeiiuent comprising. hydrocarbons and' theaforesaidvolatilederivative-of arsenic, and contact ing'v at a temperaturehigher than440?"F.` saidlre'a'cton zone eiuentwith -in'ely' divided 'solid' adsorbent.

2lv The-method of removing arsenic'from a-hydocar-- 'oon mixture as'set forth in claimel wherein the finely? dividedsolid adsorbent is hydrated aluminrun-magnesium'f silicate.

31 The methodVoffremovingvarsenicfrom a hydrocarbon mixture-asset 'forthin claimllwherein the'n'ely' divided-'adsorbentisAttapulgusclayn 4: The methodfof 'removing arsenic fr'om aI h'ydroicar bonemixtu're as'iset 'forth fin claim 'al wherein thel hydro# geua'ting;ca't'aly'vs'tcomprisesirefact'ory oxde'fsupportandf -hydrogenating 'components 7i' the: method of 'reformingr naphthaf contain'ng7 more' an.;11.p.p;m.=ot nitrogenwvhereinfnaphthafcontain ing in s excess eof` lp;p.'m; :ofi-'nitrogen is hyd'rodenitr'o genizedatlal'temperature inf.excess1ofr`440"F. in'rthe'presff ence'iofhydroge'n a'nd hydrogenation catalyst I having Shy# drodenitrogenizing ."capability; wherein f reformer: charge stockcomprising 'C51 and' 'heavier hydrocarbonsf;containingnot more ithanxl ..p.'p.-m. of: nitrogenf-is produced, .andff wherein fsaidreformeri 'charge stockV isf'reformed in; the".1 presencel of. particle-form solid nitrogenandarsenice" sensitivezreforming'catalyst the. improvementiwhich com-.- prisesLprior. to-.hydrodenitrogenizing naphtha containing rnore :than .0.002 p.p.rn'. Vof arsenic, contacting said naph tha in i a :reaction zone.: at'catemperature in'. the :range` of'f about .200? to 425 F: .with :hydrogenating catalyst capa-` ble of. converting said larsenic .to :volatile lhydrogenlderivativerthereof'atfapressure'of at least 100"p;s.i.g., atfaliquid hourly space velocity'notin excessoffabout 10, and'withfacirculationof attleastrabout*350's.c.f. of hydrogen per! 6U barrel ofarsenic containing naphtha, producing ay reac- The major portion of the stab'ilizer'bottoms ilowsfrorn tion zone efuent having atemperature below about 440" F. comprising' hydrocarbons and volatile hydrogen -deriva'- tiveof arsenic, in a sor'ptionzoneat @temperature of'at least 440 F. contacting -said reaction zone efliuent with finely, divided adsorbent; and. producingl sorption' zone' eiuent comprising.hydrocarbons'the C5 and heavierfof which have. substantially reduced content of arsenic.v

8. In themethod of reforming naphtha -setforth in= claim 7 wherein thezvirgin hydrogenation catalystI in the reaction zone and the hyd'rodenitrogenizing catalyst'each comprises a mixture of oxides ofcobalt and molybdenum on alumina support.

9. In the methodv of reforming naphthaset forth inl claim 7 wherein the virgin hydrogenation catalyst inithe- .reaction zoney and the hydrodenitrogenizing catalyst each;

comprises a mixture of oxides of cobalt and molybdenum, and wherein the uitrogenand arsenic-sensitive particleform reforming catalyst comprises platinum-group metal on alumina support.

l0. In the method of reforming naphtha in the presence of nitrogen-sensitive particle-form reforming catalyst wherein naphtha containing more than 1 p.p.m. of nitrogen is hydrodenitrogenized in the presence of hydrogen and hydrogenation catalyst having hydrodenitrogenizing capability at a temperature in excess of 440 F., wherein hydrodenitrogenized C5 and heavier hydrocarbons containing more than p.p.m. of nitrogen are mixed with naphtha containing less than 1 p.p.m. of nitrogen to form a naphtha mixture containing more than 1 p.p.m. of nitrogen, wherein said napththa mixture is hydrodenitrogenized at a temperature in excess of 440 F. in the presence of hydrogen and hydrogenation catalyst having hydrodenitrogenizing capability, wherein reformer charge stock comprising C5 and heavier hydrocarbons and containing not more than 1 p.p.m. of nitrogen is obtained, and wherein said reformer charge stock is reformed in the presence of arsenicand nitrogen-sensitive particleform solid reforming catalyst, the improvement which comprises prior to hydrodenitrogenization contacting naphtha containing more than 0.002 p.p.m. of arsenic with hydrogenating catalyst in a reaction zone at a temperature in the range of about 200 to 425 F. under at least 100 p.s.i.g. pressure, at a liquid hourly space velocity not in excess of about 10, and with a circulation of at least about 350 s.c.f. of hydrogen per barrel of arseniccontaining naphtha, producing a reaction zone euent comprising hydrocarbons and volatile hydrogen derivative of arsenic, and having a temperature below about 440 F., contacting said reaction zone effluent in a sorp- 14 tion zone at a temperature in excess of 440 F. with nely divided solid adsorbent, producing sorption zone efuent comprising C5 and heavier hydrocarbons substantially devoid of volatile hydrogen derivative of arsenic, and recovering C5 and heavier hydrocarbons of substantially reduced arsenic content.

11. In the method of reforming naphtha as set forth in claim 10 wherein the virgin hydrogenating catalyst comprises a mixture of oxides of cobalt and molybdenum on alumina support.

l2. In the method of reforming naphtha as set forth in claim 10 wherein the virgin hydrogenating catalyst each comprises a mixture of oxides of cobalt and molybdenum on alumina support, and wherein the arsenicand nitrogen-sensitive particle-form solid reforming catalyst comprises platinum-group metal on alumina support.

13. In the method of reforming naphtha as set forth in claim 10 wherein the virgin hydrogenation catalyst each comprises a mixture of oxides of cobalt and molybdenum on alumina support, and wherein the arsenicand nitrogen-sensitive particle-form solid reforming catalyst comprises about 0.35 to about 0.6 percent by weight of platinum on alumina support.

References Cited in the le of this patent UNITED STATES PATENTS 2,728,710 Hendricks Dec. 27, 1955 2,854,399 Weller et al Sept. 30, 1958 2,867,577 Urban et al. Jan. 6, 1959 2,910,434 Hess et al Oct. 27, 1959 2,937,134 Bowles May 17, 1960 2,939,833 Wankat et al .Tune 7, 1960 2,954,339 Beavon Sept. 27, 1960 UNITED STATES PATENT OFFICE CERTIFICATE OF CORRECTIGN Patent No., 3,069,350 December 18, 1962.

Amilcare Ramella 1t is hereby certified that error Yappears in the above numbered patent requiring correction and that the said Letters Patent should read as '2 *"'fcorrected below Column 14, lines 13 and 19, strike out "each", each occurrence.

Signed and sealed this 5th day of November 1963.

ISEAL) test:

EDWIN L. REYNOLDS LINEsT w. swIDER Iestmg Officer Ac ting Commissioner of Patents 

1. A METHOD OF REMOVING ARSENIC FROM A HYDROCARBON MIXTURE WHICH COMPRISES IN A REACTION ZONE CONTACTING A HYDROCARBON MIXTURE CONTAINING ARSENIC WITH HYDROGENATING CATALYST UNDER CONDITIONS OF PRESSURE, LIQUID HOURLY SPACE VELOCITY, HYDROGEN CIRCULATION, AND AT A TEMPERATURE NOT HIGHER THAN ABOUT 425*F. AT WHICH ARSENIC IS CONVERTED TO A VOLATILE DERIVATIVE OF ARSENIC, WITHDRAWING FROM SAID REACTION ZONE AT A TEMPERATURE BELOW 440*F. A REACTION ZONE EFFUENT COMPRISING HYDROCARBONS AND THE AFORESAID VOLATILE DERIVATIVE OF ARSENIC, AND CONTACTING AT A TEMPERATURE HIGHER THAN 440*F. SAID REACTION ZONE EFFUENT WITH FINELY DIVIDED SOLID ADSORBENT. 